Lazurite


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Related to Lazurite: Lazarus

lazurite

[′laz·ə‚rīt]
(mineralogy)
(Na,Ca)8(Al,Si)O24(S,SO4) A blue or violet-blue feldspathoid mineral crystallizing in the isometric system; the chief mineral constituent of lapis lazuli.

Lazurite

 

(lapis lazuli), a mineral of the silicate subclass with a skeletal crystal lattice structure similar to that of sodalite. The chemical composition of lazurite is (Na, Ca)8[A1SiO4]6-(SO4 Cl, S)2. The mineral crystallizes in the isometric system, but crystals are rare. Most commonly it is granular or in compact masses of dark blue, violet, or greenish blue color. The hardness is 5.5–6.0 on Mohs’ scale, and the density is 2,380–2,420 kg/m3. Lazurite occurs in crystalline limestones along the contact boundary between the latter and alkaline syenites in association with pyrite, glaucolite, and other minerals. The largest known lazurite deposits are in Afghanistan (Badakhshan). In the USSR there are deposits in the vicinity of Lake Baikal and in the Tadzhik SSR. Lazurite is a valuable ornamental material and is also used in the preparation of the blue pigment ultramarine.

References in periodicals archive ?
It is isomorphorous with lazurite but does not contain sulfide ions.